I can turn it on and off just fine with the HDMI input being used.
Just to be sure, I even tried to turned it off while hiding the remote in a black pillow so as to not allow any IR light to still get to the PPM, and sure, it turned off alright. It returns briefly to the Android home menu to show you the Powering off animation, and then shuts down.
Remember though that to prevent accidental turning off of the projector, you have to press and hold the power button on the remote for at least 2 seconds. Perhaps you’re pressing it too short?